In recent optical communication technology for transferring data using optical carrier wave, optical waveguide has been disseminated as a means for guiding the optical carrier wave from one location to another location. The optical waveguide has a linear core section, and a cladding section provided so as to surround the core section.
A known optical waveguide is found, for example, in Patent Literature 1. Patent Literature 1 describes an optical waveguide having the refractive index of the core section concentrically distributed when viewed in the transverse cross section, which was established by allowing a refractive index adjusting agent to diffuse in a base polymer. It is also described that the refractive index of the cladding section, which surrounds the core section, is kept constant. The core section is composed of a material substantially transparent to light used as the optical carrier wave, whereas the cladding section is composed of a material having the refractive smaller than that of the core section.